The introduction of diesel traction brought the railways into close
contact with development work for road vehicles and
marine craft. This was in contrast to steam where development tended to be
isolated, except for a few experiments with turbines or condensers which
were usually related to naval advances. The Sentinel products were major
exceptions as they formed an extension of the
Company's interest in steam road
vehicles.
The Sentinel railcars and locomotives
incorporated small, vertical water-tube boilers which powered
multiple-cylinder, high speed enclosed engines. The cylinders were actuated
by poppet valves and the final drive was either by chain or cardan shaft.
A few units were constructed with Doble, high performance
boilers.Hughes & Thomas is the key reference
where it is noted that the chain drive obviated pounding and nosing. The
company produced some excellent promotional literature at its London Office:
some of this is listed below. Lowe estimated
that 7000 of the highly distinctive engines were produced, but the
majority were used in road vehicles.

W.J.K. Davies. Light railway notes.Rly
Wld, 1963, 24, 232-4.
Sentinel articulateds for narrow gauge. 3ft gauge Sentinel WN 6412/1926 ordered by Kettering Iron & Coal
Co. Another, incorporating modifications (WN 7238/1927) was supplied to W.A.
Smith's sugar plantations in South Africa and was more successful and in
1928 WN 6412 was returned to Sentinel for modification, after which it worked
on the Thorpe Malsor branch until it closed.

Locomotives 0-4-0T Several contemporary references are listed below. sub-division has
not been attempted as a number of parameters could have been used, none being
applicable throughout. Lowe notes that
approximately 850 steam locomotives were constructed between 1923 and
1957

A GEARED shunting locomotive. Engineer, 1925, 139, 432-4; 436.
6 illus., 6 diagrs., plan.Includes detailed sectionalized diagrams.
"SENTINEL" geared locomotive. Loco. Rly Carr.Wagon Rev., 1950,
56, 172-3. ilIus.This series was not purchased by any British main-line system, but
it does show that the type was available after WW2..

Wisbech & Upwell Tramway locomotive (Y10)This is one of the odder locomotive stories. The double ended locomotives
were clearly intended for the Wisbech & Upwell Tramway (there is even
a photograph of one with that appellation painted on it, but were equally
obviously unsuccessful, and spent most of their lives on the Yarmouth street
tramways (not the Corporation electric trams)

Fell, G. The Wisbech & Upwell
Sentinels. Rly Wld, 1982, 43,. 521-3.Ordered by the LNER in November 1929 the two Y10 class locomotives
were intended for use on the Wisbech & Upwell Tramway where the former
GER tram locomotives of LNER classes Y6 and J70 were the normal motive power.
The 200hp locomotives were similar to two locomptives deleivered to the Somerset
& Dorset Railway at about the same time but the LNER locomotives were
fitted with skirts and cowcatchers for tramway operation (A works photograph
shows one un-numbered locomotive with "Wisbech & Upwell Tramways" applied
to the side skirts. One, or both locomotives were tested on the line between
11 June 1930 and 30 May 1931. Thereafter, the locomotives spent most
of their time on the quays at Yarmouth, although 8404 was sent to Scotland
in February 1934 and was tested on the lines in Aberdeen docks and
briefly at St Leonard's Yard in Edinburgh, but was back at Yarmouth in May.
Reasons for the failure of the locomotives on the Wisbech & Upwell Tramway
are discussed with reference to the appropriate volume of the
RCTS History of locomotives of the LNER
Part 9B and The Wisbech and Upwell Tramway by Gadsden, Whetmath
and Stafford-Baker. There appear to be no photographs of the locomotives
working at Wisbech, but are relatively common of working on the street lines
in Yarmouth, although this article only includes view of them on shed at
Vauxhall.Goodyer, W. The Wisbech and Upwell Tramway. Rly Mag., 1937,
81, 82-7. 2 illus., 2 maps. Includes brief notes on the Sentinel tramway locomotives. Gadsden, E.J.S., Whetmath, C.F.D. and Stafford-Baker, J. The
Wisbech and Upwell Tramway. Teddington (Middx.), Branch Line Handbooks,
1966. 51 p. + front. + 2 folding plates. 30 illus., 3 diagrs., 3 tables,
6 col. plans, 2 col. maps. Includes notes and a sectionalized diagram of the Y10 class tram engines.
Hawkins, Chrisand George Reeves. The Wisbech
& Upwell Tramway. Bucklebury: Wild Swan, 1982. 56pp.Includes 0-6-0T and 0-4-0T tram locomotives (latter restricted mainly
to passenger traffic) and very brief mention of Y10 Sentinel tramway
lcomotives.
[Hawkins, Chris] Some new notes: early trials and tribulations of
running the Wisbech and Upwell Tramway. Br. Rlys. ill., 1995,
4, 530-45.Mainly the difficulties faced with the local authorities. Includes
a photograph of standard Sentinel locomotive No. 8401 with J70 tram locomotive
on passenger train on 4 May 1927, (A. Garraway)Hoole, K.. Sentinel locomotives.
Rly Wld, 1958, 19,
235-40.Surveys all the British main line railway Sentinel locomotives using
the LNER purchaese as the yard stick. The LNER initial purchase was instigated
by the acquisition of a Sentinel locomotive by the Derwent Valley Light Railway
and the testing of this unit with the assistance of the LNER dynamometer
car in May 1925. The LNER purchased similar units and classified these as
class Y1 starting with Sentinel WN 6170/1925 which carried running number
8400. Many of this initial batch were employed aservice locomotives, such
as No. 8401 at the Lowestoft sleeper depot and No. 44 at the Faverdale Wagon
works. The locomotives had vertical water tube boilers operating at 275 psi
and vertical cylinders. Firing was simple using a small domestic-sized shovel
of the type used to feed domestic boilers. The boiler tubes were cleaned
with steam which was blown up through the boiler and out of the chimney:
the exhaust began black and tuned to white. The Y3 type differed in having
two gear ratios and the means to switch between them. In other respects they
were identical to the Y1 type: all were initially supplied for the running
stock, but later some became service locomotives.Nos. 81 and 90 were fitted
with vacuum ejectors and tested on passenger services between Seamer and
Pickering in June 1928. Other locomotives were also fitted with vacuum ejectors.
Steam and counter pressure braking were standard faetures. The Y10 double
ended Sentinels, with two speed gearboxes were built for the Wisbech &
Upwell Tramway, but were not successful and were transferred to Yarmouth
to work on the quayside. They had foot-operated gongs, govenors to limit
speed, skirts over the wheels and cow catchers. The LMS purchased four of
the Y3 type (that is two-speed) and were given running numbers 7160-3. Two
similar to the Y10, but with a single cab were built in 1929 for the Somerset
& Dorset Joint Railway and were of restricted height. Sentinel WN 7587/9
were initially 101 and 192 but became LMS Nos. 7190-1. Sentinel WN 8593/1932
RN 7164 was s short wheelbase and light machine purchased for working at
the Clee Hill quarry where it had to be hauled up and down a rope-worked
incline. Sentinel WN 8805/1934 was built for the LMS and numbered 7192: it
had a Doble boiler and was oil fired and was intended to be compared with
early diesel shunters. It was withdrawn in 1943. The GWR owned a solitary
Y1 type unit bought in 1926 numbered 13 which worked at the Park Royal Trading
Estate, but was moved to Bridgwater in 1945. Illustrations: Y1 No. 8400;
Y3 No. 117 at Hull Springhead on 21 June 1931; Y10 works photograph; Y3 No.
68169 in scrap yard at Doncaster on 17 July 1955: LMS No. 7164; LMS No. 7160;
LMS 7192 with diesel No. 7051; and SDJR No. 104.Middlemass, Tom. Tram traction from Wisbech.
Rly Mag., 1983, 129, (988)
315Includes mention of ten months spent by Sentinel Y10. Written at the
end of the Wisbech & Upwell Tramway.
{Mitchell, Vic, Smith, Keith} and Ingram, Andrew C.Branch line
to Upwell. Midhurst: Middleton Press, 1995. 96pp.It would appear that Andrew Ingham was the "real" author. Book is
interesting for containing photograph (figure 27 taken by W. Whitworth) of
Y10 Sentinel tram locomotive No. 8404 taken at Wisbech. Figures 27,
43 and 111 show experiments with Sentinel Y1 No. 8401 on passenger workings
on 4 May 1927, both at Wisbech and at Upwell. White, Malcolm. The Yarmouth
train. 2005.Some highly interesting photographs of the Y10 Sentinel locomotives
working on the quayside tramway system, including one visiting the Lacon
Brewery in 1936.

Tests

Hughes and Thomas quote tests on the LNER, which
initially purchased one Sentinel GE. type on the maker's statement that it
would save 50 per cent on coal, oil, stores, and maintenance. This was No
6170, new in January 1926. The results were so promising that three more
were purchased in June, and by 1931 there were 55 Sentinel locomotives on
the LNER.

An early official report of this railway stated:

The 100 H.P. 'Sentinel' engines are being used in replacement of
ordinary steam engines employed on regular shunting work at Victoria Dock,
Hull, at Pickering and at Goole. So far the engines are doing well and have
enabled economies to be made which will be sufficient to write off the
capital cost in less than two years. [Hughes & Thomas italics]

On another use for the Sentinels, shunting at wayside stations, the
report said

On the pick-up working between Hull and Selby three freight train
engines were employed, one working a pick-up from Hull to Brough and returning
as a Class B through goods; another working a pick up from Selby to Brough
and back, and the third engine proceeding light from Selby to Staddlethorpe,
whence it worked a pick-up to Selby. By using a 'Sentinel' engine for
intermediate shunting it was found possible to re-arrange the whole of the
pick-up working so that in place of the three train turns previously mentioned
there are now only two. . . . In this case and in that of a similar experiment
on the Hull and Barnsley section the 'Sentinel' engine is also making economies
in working costs sufficient to pay for itself within two years. [their
italics again.]

Burgess, Neil. Somerset & Dorset
Sentinels: a consideration of their place in LMS locomotive history.
Backtrack, 2004, 18, 327-331.S&DJR 0-4-0T Nos, 101 and 102 (BR 47190 and 47191). In some respects
the purchase was rather surprising: Radstock in which the locomotives
spent most of their time was an economic backwater at that time and the LMS
was disposing many of its L&YR 0-4-0STs, some of which saw further service
in industry. The Author suggests that the purchase may have reflected a more
general evalution, especially as 7191 spent the three years, 1932-5, at Kettering
and was at Highbridge from 1942-4 (KPJ but this may have reflected a shortage
of . spare parts during WW2. The locomotives were 200hp with double engines
and could be single-manned. John Edgington
provided corrections to table (see page 443). Many references.
Thorley, W.G.F. A breath of steam.
Vol. 1. London, 1975. Page 95:Sentinel. One of the latter, No 7191, was
allocated to Kettering to shunt in the large goods yard there and I [Thorley]
was despatched more than once to fit a new firehole door to its vertical
cross-tube boiler. My recollection is that the door was made from some alloy
material which fractured rather easily and the door itself required to have
a good seating on the firebox shell plate.

This is not a very happy sub-division, but the article featured does
show the highly distinctive WN 6412/1926 built for the 3ft gauge Kettering
Iron & Coal Co. A table compiled from the Company's official records
shows narrow gauge locomotives produced for United Kingdom customers. WN
7700 for the London Brick Company's clay pits at Stewartby clearly shows
how the driver was shoe-horned into the low headroom 2ft 11in gauge
locomotive.

Railway Correspondence & Travel
Society.Locomotives of the LNER. Part 10A. Departmental stock, locomotive
sheds, boiler and tender numbering. 1990?.. The self-propelling ash cranes are difficult to find, but are considered
on page 19 under Scottish Area. There were two of these Sentinel Works Number
8157 (LNER 773044) and WN 8565 (773066). They were not regarded as locomotives
yet were required to travel on running lines and were passed to run at 24
mile/h. The former worked at Eastfield and Parkhead in Glasgow where it was
known as Stoorie Annie. The latter worked between Haymarket and St
Margarets (but there were problems with track circuits), and later at Dundee
and Thornton. Figures 53-5. The cranes were supplied by Henry J. Coles of
Derby and had their own engine.

1923 Original design with chain drive. The first units were bought by the Jersey Railways
(see also histories of Channel Islands railways). According to
Hughes & Thomas Works Number 4863 of June 1923
and named The Pioneer was used on the 3ft 6in gauge Jersey Railways
and Tramways between St Helier and St Aubins and Corbière. The passenger
car was pivoted to the power bogie and the joint was filled with fireproof
leather sides to form a flexible connection with a steel plate on the top.
The wheels had rubber inserts to reduce noise and vibration. Coal consumption
was 4lb/mile and water consumption 2½ gal./mile. The vehicle was noted
for its smooth running. By June 1931 the unit had run 200,000 miles. WN 5759
was delivered in January 1924 and WN 5833 followed in March 1925. The Jersey
Eastern Railway acquired a standard gauge railcar WN 5655 in March 1925.
See also paper by Kelway-Bamber.

LMS railcarsAccording to Hughes & Thomas these were
WN 6177-88. They also cite Railway Gazette for "December" 1927 to note that
all these vehicles were in service in Scotland, although originally envisaged
for North Wales and Anglesey, the Wirral, the West Riding and the Southport
area as well as Scotland.

Other materialSome of the older material, especially that by Kidner, is probably
now of dubious value

Bowtell, H.D.and Cook. A.F. The steam railcars of the L.N.E.R..
Railways, 1950, 11,179-80. 3 illus.A stock list. Bradley, D[onald] L[aurence]Locomotives of the Southern Railway. London, 1975. Volume 1.Pp 71-2 briefly survey the Southern railbus No. 6 ans the Drewry railcar
No. 5.The LNER railcars in Scotland. C.S.
Carter and A.R. Maclean. Br Rly J., 1987, 2, 275-9.Includes note that there was a suggestion within the Scottish Area
that railcars should be painted deep blue all over. Lines operated included
Stirling to Balloch; Aberfoyle and Blanefield; Kinross Junction to Alloa
and Ladybank; Stirling to Alloa, Alva and Dollar [KPJ Menstrie in 1946];
Thornton Junction and Methil; Hamilton to Blairhill and Shettleston; Edinburgh
District to several destinations, including Dalmeny and Ratho; North Berwick,
Dunbar, Penicuik and North Leith as well as Galashiels to Selkirk; Carlisle
District to Port Carlisle and to Silloth; and Aberdeen District from Aberdeen
to Culter and Banchory and to Dyce and Ellon.. See letter
from K. Hoole in Number 17 page 351 which indicated several errors. Illus.:
No. 33 Highland Chieftain at Ellon; No. 313 Banks of Don at
Thornton Junction in June 1934; No. 31 Flower of Yarrow on St Margaret's
shed; No. 39 Protector at Langholm. Mileages achieved are
quoted..Coleford, I.C. Sentinel railcars. Br. Rlys ill., 1994,
3, 529-39; 624-34.History of the development of the Sentinel railcars, mainly on the
LNER. Development included the fitting of deflector plates alongside the
chimney to stop smoke entering through the windows of the car. Includes
observations on names for cars, notably those of stagecoaches. Like many
articles in this journal there are quotations from official documents which
give an aura of "authenticity". The second part contains several illustrations
of (1) the CLC vehicles in two of which the chocolate and buff livery is
clearly visible (albeit not in colour); and (2) the cars painted brown during
WW2Earnshaw, Alan. Lines to the [Carlisle]
Citadel. Backtrack, 1997, 11, 531.page 531 Sentinel Rail Car Nettle on 16 Sept 1931 (caption
notes that tail loads of three vans or two coaches sometimes hauled on the
lines to Langholm and Silloth). Edgington, T.J. Railcars on the LMS.
Backtrack, 2001, 15, 696-8.Lists some of the routes on which Sentinel railcars worked, including
Strathpeffer branch; the Ayr to Girvan line via Turnberry,; Wanlockhead and
Horwich branches. Illus.:LMS Sentinel railcar No 2233 at Perth in 1932, Sentinel
railcar No 4144 ex-works (Erratum (date)
on page 114 Vol. 16), Sentinel railcar No 4151 at Hamilton Central, Sentinel
railcar No 4349 at Hamilton shed in 1933, List of Allocation of Sentinel
railcars and workings in 1932. Most withdrawn in 1935.
EXTINCT locomotive classes the London and North Eastern "Y3" class Sentinel
0-4-0's. J. Stephenson Loco. Soc., 1958, 34, 113-14. Hardy, R.H.N. Railways in
the blood. Ian Allan, 1985.Page 15: firing a Sentinel on the 1 in 38 gradient out of Batley 'Oil
with stops at Upper Batley and Howden Clough on climb to Drighlington: "if
we started to slip all hell was instantaneously let loose"Hoole, K. Railcars in the North-east. Rly Wld, 1957,
18, 257-61. 12 illus. An account of the Sentinel types and of the Armstrong Whitworth diesel
electric cars.Hoole, K. Sentinel locomotives. Rly Wld, 1958, 19,
235-40. 9 illus., 3 tables. Restricted to the products used on the British main-line
railways.Hoole, K. The Sentinel railcars and locomotives of the L.N.E.R..
Rly Obsr, 1952, 22, 150-3; 175-8; 209-10; 240-2; 319-20 + 5
plates. 16 illus., 8 tables. Errata :1953, 23, 54; 147. Hughes, W.J. and
Thomas, Joseph L. 'The Sentinel': a history of Alley & MacLellan
and The Sentinel Waggon Works. Volume 1. 1875-1930. 1973. .This is a vital source of information about (1) the
Company and (2) the development of the
road steam lorries which were to greatly influence
the development of the railway locomotives and steam railcars described herein.
There is a section where the authors infer that Kyrle Willans may have been
influential in directing Sentinel towards locomotive development citing a
reference to an article by L.T.C. Rolt in Old Motor (but this aspect
is covered in Rolt's Landscape with
machines.Jenkinson, David and Lane,
Barry C. British railcars, 1900 to 1950.1996.Chapter 4: A second chance for steam: pp. 46-57. Mentions but does
not illustrate Jersey vehicles and excludes Irish vehicles. Kidner, R.W. Multiple unit trains, railmotors and tramways, 1829-1947
in : Kidner, R.W.A short history of mechanical traction and travel. v. II: Rail.
Chislehurst (Kent), Oakwood Press, 1947. [vi] 150 p. + front. + 39 plates.
354 illus. (incl. 260 thumb-nail skitches). Bibliogs.The main reference consists of four separate works, most of which
(but not this part) were also published separately. This part (pp. 107-50)
has its own bibliography.Kidner, R.W.The railcar, 1847-1937. Sidcup (Kent), Oakwood
Press, 1939. 65 p. + 6 plates. 116 illus. (incl. 99 thumb-nail sketches),
7 tables.includes a chapter on Sentinel and other steam geared
railcars.Klapper, C.F. Derwent Valley Light Railway. Loco. Rly Carr. Wagon
Rev., 1929, 35, 50-3. 5 illus.Includes details of economies which resulted from the use of a Sentinel
locomotive.Lathey, G. The hunting of the 'Steam
Pig'. Backtrack, 1996, 10, 78-80.Workings of Sentinel railcar 51914 Royal Forrester in the Leeds
area during 1936/1937. Letter (page
278) claims same car worked Hertford to Hitchin.
Brian Orrell (page 222) had
not heard expression Steam Pig used for Sentinel railcars in Wigan/St
Helens area where they were known as the Chip Train. and back;
L.M.S.R. Sentinel railcar withdrawn. Rly Gaz., 1940, 72,
394. No. 29913 : final survivor (100 h.p.cardan drive
type).Maggs, Colin. The branch lines of Gloucestershire. Amberley
Publishing. information gleaned from review by RH (Roger Hennessey?)
in Backtrack, 2012,
26, 443."the author finds room for many intriguing asides, such as the Sentinel
railcar that the GWR tried out on the Tetbury branch"Oates, G.The Axholme
Joint Railway. 1961. (Locomotion papers, No. 16).The Axholme Joint line nominally possessed one Sentinel
railcar.Railway Correspondence & Travel
Society. The locomotives of the Great Western Railway. Part 6.
Four-coupled tank engines. 1959.No. 12 had an extremely short life whilst No. 13 lasted until 1946.
Both entered service in 1926, but the former was withdrawn almost immediately.
No. 13 is illustrated.Railway Correspondence &
Travel Society. Locomotives of the LNER. Part 9B. Tank
enginesclasses Q1 to Z5. 1977. LNER classes Y1, Y3 (covered together) and Y10. Lowe indicated that
the Sentinel locomotives were fitted with counter pressure braking: this
is also recorded herein. Commentators on counter pressure braking have probably
failed to note this exploitation of the system (it appears to have been standard
practice on both the locotives and on the road vehicles).Railway Correspondence & Travel
Society. Locomotives of the LNER. Part 10A. Departmental stock, locomotive
sheds, boiler and tender numbering. 1990?.. Some Y1 and Y3 types as painted in Departmental Stock series are
illustrated. The self-propelling ash cranes are difficult to find, but are
considered on page 19 under Scottish Area. There were two of these Sentinel
Works Number 8157 (LNER 773044) and WN 8565 (773066). They were not regarded
as locomotives yet were required to travel on running lines and were passed
to run at 24 mile/h. The former worked at Eastfield and Parkhead in Glasgow
where it was known as Stoorie Annie. The latter worked between Haymarket
and St Margarets (but there were problems with track circuits), and later
at Dundee and Thornton. Figures 53-5.Railway Correspondence & Travel
Society. Locomotives of the LNER. Part 10B. Railcars and electric
stock. 1990. 150pp. Includes Sentinel and Clayton steam railcars which were numbered with
the carriage stock: this latter causes difficulties for the researcher as
less information wass available on carriage transfers.Read, R.E.G. Good-bye to the steam railcar. Trains ill.,
1949, 2, 50-2. 5 illus. Rolt, L.T.C.Landscape with machines. 1971.Now available within The landscape trilogy. 2001. This shows
Rolt's involvement with a Sentinel agricultural tractor, and with his observation
of Kyrle Willans' reconstruction
of a Manning Wardle at Blackwells engineering works in Northampton in 1922.
An industrial locomotive became in effect the first Sentinel locomotive by
using the chassis of Ancoats (owned by the Isham Ironstone Co) combined
with boiler , engine and chain drive from a Sentinel lorry. The Ironstone
Company was very impressed by the locomotive's performance. On page 92 Rolt
noted that Kyrle Willans' work for Sentinel had made him very conscious of
the shortcomings of the Sentinel boiler. Rolt was also well aware of the
limitations of the Sentinel boiler whilst using th Sentinel agricultural
tractor at Pitchill. Later Rolt encountered Abner Doble at the Sentinel Works.
The flash steam waggon was capable of doing the round trip from Shrewsbury
to Glasgow and back in less than twenty four hours.Rutherford, Michael. Bogie
steam locomotives - Part 2. [Railway Reflections No. 42]. Backtrack,
1995, 9, 183-90.Describes the bogie locomotive developed for Colombia and tested in
Belgium where it was demonstrated to Gresley, Bulleid, Clayton,
Stanier and Hawksworth.Rutherford, Michael. Was
there a future for steam? - Part 1. [Railway Reflections No. 4].
Backtrack, 1995, 9, 183-90.This part was mainly concerned with the development of high performance
steam engines for road vehicles, and the adaption of this technology to railway
traction. Stephen Alley was the
founder of the Sentinel operation associated with steam road and railway
vehicles. and development might have gone much further had the financial
state not been so severe during the 1920s and 30s, specially once Doble became
involved in the firm. Doble's best known contribution was to high performance
steam automobiles, but similar technology was applied to a railbus for the
Southern Railway and a locomotive for the LMS. The author also mentions Kyrle
Williams advanced water tube boilers, but the work ended with the failure
of Kerr Stuart, and the Swiss Locomotive Company's high pressure locomotive
with double acting Uniflow cylinders with jackshaft drive and the
application of the Woolnough marine water tube boiler to Sentinel railcars.
Rutherford, Michael. Some reflections
on the narrow gauge. Part 4. (Railway Reflections No.132). Backtrack, 2007,
21, 437-46.Includes accounts of the performance of Sentinel-Cammell railcars
in the Peruvian Andes via Brian Fawcett's Railways of the Andes and
of the use of oil-fired locomotives on the Egyptian Delta Light Railways
and on the 2ft 6in Barsi Light Railway in India which:incorporated
Everard Calthrop's ideas for very
light axle loads. Includes diagram of the metre gauge bogie locomotives supplied
to Colombia in 1934.White, Malcolm. The Yarmouth
train. 2005. page 70 upperLNER Railcar Tantivy photographed at one of the camp
halts.on the M&GNJR between Stalham and Yarmouth Beach
during the summer of 1933: it carried 22,276 passengers between 17 July and
19 September
[WITHDRAWAL of LMSR. Sentinel railcar No. 29913]. Loco. Rly Carr. Wagon
Rev., 1940, 46, 83.

The Super-Sentinel Waggon (lorry) was introduced in April 1923 at
about the same time that the company started to manufacture locomotives and
railcars. In many respects these vehicles were at least comparable with
contemporary internal-combustion-engined trucks.

Alley and L.E. Slade 222,955 11 July 1923 Works number 5156 July 1923 for 750 mm gauge.

Central engine type (CE)
Alley 239,932 18 June 1924 Unlike the road vehicles the locomotives lacked a differential and
the velocity in reverse was identical to that in forward.

Double engine (DE)
248,835 December 1924 Each engine drove a separate axle, and the patent allowed for multiple
boilers and for articulation, but usually a 200 hp boiler supplying 4600
lb steam/hour was employed. It was to large for top firing and had a firedoor
just above footplate level. A squared firebox was used and was not supplied
by Galloways as this firm had gone out of business.

From March 1925, and possibly before, the locomotive version
of the engine was redesigned for greater efficiency and economy in the valves,
but the modifications could not be applied to road vehicles because of lack
of space.

Unlike most other locomotive manufacturers this company did not set
out to manufacture locomotives or steam railcars, but had its origins as
'The shipyard on dry land' (J.G.R. Woodvine Introduction to Hughes). This
shipyard began in Bridgeton in Glasgow and moved to Polmadie (better known
to railway enthusiasts as the location of a major motive power depot. The
major instigator of this concern was Stephen
Alley, but it was his son, Stephen
Evans Alley, who brought the firm capable of manufacturing locomotives
and railcars into being.

The Sentinel Engineering Works had been founded by Alley senior in
association with John Alexander MacLellan in 1875 in Bridgeton, Glasgow,
and the firm moved across the Clyde to Polmadie in 1880. The firm built
prefabricated ships and engines for paddle steamers and marine auxiliary
machinery. In 1905 the firm bought its way into steam by buying the rights
of Simpson & Bibby and moving
the key people to Glasgow where the Sentienl Steam Waggon was developed.

In 1915 this activity was moved to a new factory at Shrewsbury alongside
the LNWR mainline to Crewe. The development included model housing for the
workforce where the factory provided hot water for domestic use including
central heating. Unfortunately, the piping corrided by the late 1920s and
gas-fired heating had to be substituted for the central source.

The boiler shells and fireboxes were supplied by Galloways of Manchester
and Abbotts of Newark. On 17 May 1918 the "Sentinal Waggon Works" came into
being with a Registered Office in Shrewsbury and independent from Alley &
MacLellan Ltd in Glasgow. Stephen Evans Alley was Chairman of the new
company

In 1925 a separate company, Sentinel Industrial Locomotives Ltd was
established with its Office in Chester and with
Arthur Thomson as its Assistant
General Manager, but this activity had to be merged with that of the Railway
Department back at Shrewsbury in 1928.

Abner Doble,
the American steam car designer, joined Sentinel briefly and this led to
the locomotive constructed for the LMS which was fired with liquid fuel and
was intended to be comparable with the internal combustion locomotives being
evaluated at the same time. It also led to the Southern railbus and to the
metre gauge locomotive for Colombia (which was inspected in Belgium by a
party which included Gresley, Bulleid and Hawksworth). See especially Trans.
Newcomen Soc., .